Conventionally, to obtain automobile parts and machine parts, a method for manufacturing a formed component by press-forming a metal plate at low temperatures has been used. In the cold press forming method, however, since the metal plate has properties such that the ductility thereof lowers with increasing strength, and therefore a break (crack) is generated, it can be difficult to obtain a pressed product having an intricate shape. In addition, even for a pressed product having a simple shape, the elastic recovery (e.g., spring back) generated by the relief of residual stress after forming can pose a problem, whereby high dimensional accuracy may not be obtained in some cases.
As a technique for obtaining high-strength formed components and formed parts, which is substituted for the cold press forming method, a hot press forming method for press-forming a heated metal plate material has been known. For the metal plate material, the ductility thereof can be increased and the deformation resistance thereof is lowered by heating. Therefore, in the hot press forming method, the problems of break and spring back can often be alleviated. However, in the hot press forming method, the metal plate (e.g., the work material) should be held at a bottom dead point for a predetermined period of time, e.g., to ensure a predetermined quenching hardness. Therefore, the hot press forming method may have a problem in that the tact time is lengthened by this holding process, whereby the productivity is likely decreased.
Accordingly, when the heated metal plate is press-formed or after the heated metal plate has been press-formed, a cooling medium can be brought into contact with the metal plate (e.g., the work material) from the die side to cool the metal plate (e.g., the work material), whereby the metal plate/work material can be quenched. By this cooling process, the time for holding the metal plate/work material at the bottom dead point can be shortened, and therefore the productivity of formed component can be improved.
As a mechanism for cooling the metal plate/work material, a mechanism has been described in which a cylindrical supply path through which the cooling medium passes is provided in the die that comes into contact with the metal plate/work material, and the cooling medium is ejected from the die surface, which is an end portion of the supply path, toward the metal plate/work material. Such mechanism has been described, e.g., in Japanese Patent Application Laid-Open No. 2005-169394.
In the above-described cooling medium ejecting mechanism, a plurality of ejection ports from which the cooling medium is ejected are provided on the die surface to enhance the cooling efficiency of the formed metal plate. In addition, by branching the supply path into several paths from one supply source in which the cooling medium is stored, the cooling medium is ejected from the plurality of ejection ports.
On the other hand, Japanese Patent Application Laid-Open No. 2002-282951 describes a hot press forming apparatus in which introduction grooves for allowing the cooling medium to flow are formed in the forming surface of die. This publication also describes a technique in which the cooling medium is supplied in the state in which a punch (e.g., a male die) is at the bottom dead point, and the cooling medium comes into contact with the work material while passing through the grooves in the forming surface, whereby the work material is cooled.
Accordingly, there may be a need to address and/or overcome at least some of the deficiencies described herein above.